Recent research progress of electrocatalytic reduction technology for nitrate wastewater: A review

Recent Progress and Perspectives on Transition Metal-Based Electrocatalysts for Efficient Nitrate Reduction

“…Charge injection is likely limited by the high energy of the nitrate’s lowest unoccupied molecular orbital, which also impacts the rate of conversion from nitrate to nitrite. Transition metals with unpaired d-electrons and similar d-band energies may facilitate the conversion of NO 3 – to NO 2 – . , Nitrite formation usually occurs through a synergistic electrochemical-chemical-electrochemical mechanism. That is, NO 3 – receives an electron to produce the unstable nitrate divalent anion (NO 3 2– ), which is subsequently hydrolyzed by a homogeneous chemical reaction to produce a nitrogen dioxide radical (NO 2 – ), which receives another electron to continue the reaction to produce NO 2 – . NO 3 − false( ads false) + 2 normalH + + 2 normale − → NO 2 − false( ads false) + normalH 2 normalO …”

“…When a moderate amount of free Cl – is present in the electrolyte, NH 4 + produced by the reduction of NO 3 – at the cathode can be oxidized to N 2 , as shown in reaction , thus improving N 2 selectivity . However, when the concentration of Cl – in the electrolyte solution is too high, the resulting ClO – can reoxidize NH 4 + to produce NO 2 – and even NO 3 – via eqs –, which can cause a lower efficiency of nitrate reduction . Cl – , which is a common ion in drinking water and wastewater to be treated, has a significant role in controlling the electrochemical nitrate reduction efficiency and improving N 2 selectivity.…”

Bimetallic Pd‐Sn Catalytic Electrodes from Deep Eutectic Solvents for Selective Nitrate Reduction Toward Nitrogen

“…[ 8 ] Electrodialysis, on the other hand, is unsuitable due to high resistance and energy consumption. [ 9 ] Chemical reduction produces sediment and sludge, which are toxic hazardous waste. In addition to aforementioned methods, there are ways to reduce nitrates using energy: electrochemical, photochemical and thermal.…”

Mixed-valence Cu-based heterostructures for efficient electrochemical nitrate reduction to ammonia

“…5 The activity and selectivity of the electrochemical NO 3 RR significantly relied on the selected cathode material. 2 Copper (Cu) is regarded as one of the most active metals for the NO 3 RR since it exhibits high current density and superior kinetics for the reduction of nitrate to nitrite. [6][7][8][9][10][11][12] This is attributed to similar d-orbital energy levels of Cu to the lowest unoccupied molecular π* orbital (LUMO π*) of NO 3 − , thereby facilitating electron transfer.…”

“…1 The electrochemical nitrate reduction reaction (NO 3 RR) has been considered as a promising technique for nitrate removal due to its facile operation, absence of secondary pollution, and high treatment efficiency. 2 Beyond addressing nitrate pollution, the NO 3 RR also provides a feasible solution for artificial nitrogen fixation under ambient conditions. The NO 3 RR involves multiple proton and electron transfers, and thus a variety of nitrogen-containing products can be obtained by this process.…”